Child kidnappings are on the increase according to recent newspaper reports. Parents, therefore, become extremely concerned about their children's safety and teach their children never to speak to any strangers on the street when going out alone or in schoolmate's accompany. Nonetheless, child kidnapping still takes place. The major reason is that the kid's self-defence ability is so weak that he or she has difficulty in making distress call. The same situation happens to women. As more and more women go out working in present society, their safety after office or job in the night becomes a matter of concern. Because of their insufficiency in distress call like the children, women are easily targeted by criminals. For these reasons children and women need to have a means to signal their distress at times of emergency.